A considerable technology concerned with high-speed winding of stator cores has developed over the years and my U.S. Pat. Nos. 2,949,789, 3,785,212 and 3,821,903 are illustrative of this development. Various means, shown in these patents, are utilized for moving the winding head and its wire-dispensing member, or needle, in a compound reciprocating high-speed stroke which is sequentially parallel to and then transverse to the axis of the stator bore to thereby place a winding around the stator poles or teeth.
Recent developments in, and broadening of, the application of various types of electrical servo devices (stepper motors are an example) have introduced complications in the winding process for these motors. Many types of specialized motors utilize stator cores of relatively small size with a relatively large number of teeth extending radially inward to define a central stator bore which is small in cross-section. The teeth are straight sided and the slot area between the radial teeth is, therefore, of circular sector configuration. In order to provide a maximum number of turns on each tooth, it is, thus, desirable to place windings on the teeth which are of varying depth--that is, varying from a minimum depth at the free, inner end of each tooth to a maximum at the base of the tooth. The circular sector configuration of the space between teeth is thereby utilized to maximum effectiveness.
The placing of such varying depth windings appears, using conventional stator winding technology, to require the imposing of a further radial movement on the winding head in addition to the sequential angular and vertical reciprocating motion necessary to produce the conventional winding. The additional radial motion imposed must, to make the matter still more complicated, be composed of a series of strokes of decreasing magnitude. Apparatus has been attempted utilizing complicated dwell gearing to provide the required added radial motion to the wire-dispensing member component of the winding head. Other apparatus has attempted to solve the problem by bodily shifting the winding head and its wire-feeding shaft in a sequenced, orbital, circular path; but this mode of operation is inhibited by the relatively small central bore (some of the order of 3/8 inch in diameter) of the stators being wound and the relatively long stator teeth. Both types of apparatus have proved to be prone to malfunctioning and, of necessity, can be operated only at relatively slow winding speeds.
The concept of the present invention provides for placing windings of varying depth on the radial stator teeth at high speed and without imposing an additional motion component on the winding head. This is accomplished by utilizing winding turn distributing elements, or shrouds, inserted from outside the stator circumference (as contrasted with the central bore of the stator). The elements move between the oscillating motion path of the wire-dispensing needle and the opposite end faces of the stator and their motion comprises a series of strokes of decreasing length. The conventional vertical motion of the winding head pulls the wire along the tapered tip of the elements depositing the wire at a location on the stator tooth immediately adjacent the tips of the shrouds. Because of their series of strokes referred to above, the shroud tips move more repeatedly over the base area of the tooth, resulting in the placing of a winding of increasing depth along the tooth with the greater thickness of the winding occurring adjacent the tooth base. This filling of the circular sector configurated space between stator core teeth with the maximum number of winding turns is accomplished without adding any additional motion component to the winding head in the central bore of the stator. Since the winding head need only perform its conventional oscillating angular motion and reciprocating vertical motion, the winding head may extend through and be actuated through the central bore of the stator core even though the bore is of relatively small diameter. Introduction of the wire-distributing elements or shrouds into the winding path from the exterior, or out-board of, the core, rather than from within its central bore, permits the depositing of windings of varying thickness in extremely limited available space such as the circular sector shaped space between the inwardly extending teeth or poles of a small stepper motor stator core. The apparatus may be operated at high speed with windings placed on the core teeth at a rate of the order of 1200 turns per minute being typical.